<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 6.5.6

Error message:
Copying files from remote side failed.

Invalid access to memory.

Stack trace:
(00D542D4) TTerminal::DoCopyToLocal
(00EF78FE)
(00EF9976)
(00EF6720) __ExceptionHandler
(000B424F) ntdll.dll
(0007AE9A) ntdll.dll.KiUserExceptionDispatcher
(00D20E82) TSFTPFileSystem::CopyToLocal
(00D53D13) TTerminal::CopyToLocal
(000D0D8D) TThumbnailDownloadQueueItem::DoTransferExecute
(00C497ED) TTransferQueueItem::DoExecute
(00C48AEE) TQueueItem::Execute
(00C47AE7) TTerminalItem::ProcessEvent
(00C45E18) TSignalThread::Execute
(000DF53B) Userinterface::C20_0
(00014D47) KERNEL32.DLL.BaseThreadInitThunk
(0006D129) ntdll.dll
(0006D0AC) ntdll.dll

Stack trace:
(000CF962) TTerminalManager::ThumbnailNeeded
(000B424F) ntdll.dll
(0007AE9A) ntdll.dll.KiUserExceptionDispatcher
(00035B54) TCustomScpExplorerForm::RemoteDirViewThumbnailNeeded
(00BB3BF0) TUnixDirView::ItemThumbnail
(0050668F) Customdirview::TCustomDirView::CNNotify
(0039E3C2) Vcl::Controls::TControl::WndProc
(003A356D) Vcl::Controls::TWinControl::WndProc
(0041B07F) Vcl::Comctrls::TCustomListView::WndProc
(003A36C7) Vcl::Controls::_17122
(003A356D) Vcl::Controls::TWinControl::WndProc
(003A2A78) Vcl::Controls::TWinControl::MainWndProc
(00204C90) System::Classes::_18364
(000383D1) USER32.dll
(00027578) USER32.dll
(0002701B) USER32.dll
(000322C7) USER32.dll
(0007AE74) ntdll.dll.KiUserCallbackDispatcher
(0003FA93) USER32.dll
(00026D41) USER32.dll.SendMessageW
(0009BCC6) COMCTL32.DLL
(0009D22C) COMCTL32.DLL
(000D1C99) COMCTL32.DLL
(0009DDCD) COMCTL32.DLL
(000930E3) COMCTL32.DLL
(00093250) COMCTL32.DLL
(0009333C) COMCTL32.DLL
(000933B7) COMCTL32.DLL
(00095A8E) COMCTL32.DLL
(00094812) COMCTL32.DLL
(000383D1) USER32.dll
(00027578) USER32.dll
(00026CE5) USER32.dll.CallWindowProcW
(003A3675) Vcl::Controls::TWinControl::DefaultHandler
(003A81FF) Vcl::Controls::TWinControl::WMPrintClient
(0039E3C2) Vcl::Controls::TControl::WndProc
(003A356D) Vcl::Controls::TWinControl::WndProc
(0041B07F) Vcl::Comctrls::TCustomListView::WndProc
(003A3FCB) Vcl::Controls::TWinControl::WMPaint
(0041CF29) Vcl::Comctrls::TCustomListView::WMPaint
(003A356D) Vcl::Controls::TWinControl::WndProc
(0041B07F) Vcl::Comctrls::TCustomListView::WndProc
(00204C90) System::Classes::_18364
(000383D1) USER32.dll
(00027578) USER32.dll
(00026CE5) USER32.dll.CallWindowProcW
(00082BA4) COMCTL32.DLL
(00082C43) COMCTL32.DLL
(000829BC) COMCTL32.DLL
(000383D1) USER32.dll
(00027578) USER32.dll
(00026CE5) USER32.dll.CallWindowProcW
(00539473) Dragdrop::TDragDrop::WndMethod
(00204C90) System::Classes::_18364
(000383D1) USER32.dll
(00027578) USER32.dll
(0002701B) USER32.dll
(000322C7) USER32.dll
(0007AE74) ntdll.dll.KiUserCallbackDispatcher
(000260AB) USER32.dll.DispatchMessageW

(001379F4) System::TObject::Free
(000B424F) ntdll.dll
(0007AE9A) ntdll.dll.KiUserExceptionDispatcher
(00

The problem happens rarely. I cannot reproduce it.